The eBay link is gone, but tmk the 160GB 1.8" drives are not compatibile and there's no adapter for them.

The F40 uses a HDD with a 50 pin adapter - the largest drive available (without using an adapter) is 80GB. With a ZIF adapter, I know that a 120GB drive will work, at least with Rockbox. Adapter details can be found here:

Good luck! It is a bit of a DIY, btw - the adapter fits very snug in the F40 case, and you need to tape it in such a way so the cable doesn't short out. But once you hit the "sweet spot", in works very well.

Again, I've only done this with the Rockbox firmware - I have no idea if the original Toshiba firmware will work.